1. Field of the Invention
The invention pertains to a chemical mechanical abrasive composition. The chemical mechanical abrasive composition is useful in polishing the surface of a semiconductor wafer.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) is a planarization technique which was developed to address the problem associated with the difficulty in focus during a photolithography process for producing integrated circuits owing to the difference in the height of deposited films. Chemical mechanical polishing technique was first applied to the production of the elements with a size in the order of 0.5 microns. With the reduction in the size of elements, the chemical mechanical polishing technique was applicable to an increased number of layers. Until the elements were developed to the order of 0.25 microns, the chemical mechanical polishing became a main and essential planarization technique. In general, the polishing method for producing a wire circuit comprises mounting a semiconductor wafer on a spinning platen equipped with an abrasive head and applying an abrasive slurry comprising abrasive particles and an oxidant to the surface of the wafer to enhance the abrasion efficacy.
U.S. Pat. No. 5,225,034 discloses a chemical mechanical abrasive slurry which comprises AgNO3, solid abrasive particles, and an oxidant selected from H2O2, HOCl, KOCl, KMgO4, or CH3COOOH. The slurry is used for polishing a copper layer on a semiconductor wafer so as to produce a copper wire on the wafer.
U.S. Pat. No. 5,209,816 discloses a method for polishing an Al- or Ti-containing metal layer with a chemical mechanical abrasive slurry. The abrasive slurry contains, in addition to a solid abrasive material, about 0.1-20% by volume of H3PO4 and about 1-30% by volume of H2O2.
U.S. Pat. No. 4,959,113 discloses a method of using an aqueous abrasive composition for polishing metal surfaces. The aqueous abrasive composition comprises water, an abrasive, e.g. CeO2, Al2O3, ZrO2, TiO2, SiO2, SiC, SnO2, or TiC, and a salt including a metal cation of Group IIA, IIIA, IVA or IVB and an anion of chloride, bromide, iodide, nitrate, sulfate, phosphate or perchlorate. This patent also discloses the use of hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid to adjust the pH of the abrasive composition to be in the range of 1 to 6.
U.S. Pat. No. 5,391,258 discloses an abrasive composition for polishing silicon, silica or silicate composite. The abrasive composition comprises, in addition to abrasive particles, hydrogen peroxide and potassium hydrogen phthalate.
U.S. Pat. No. 5,114,437 discloses a polishing composition for an aluminum substrate comprising an alumina polishing agent having an average particle size of 0.2 to 5 xcexcm, and a polishing accelerator selected from the group consisting of chromium(III) nitrate, lanthanum nitrate, ammonium cerium(III) nitrate, and neodymium nitrate.
U.S. Pat. No. 5,084,071 discloses a chemical mechanical polishing slurry for an electronic component substrate. The polishing slurry comprises no more than 1 weight percent of alumina, abrasive particles (e.g. SiO2, CeO2, SiC, Si3N4, or Fe2O3 particles), a transition metal chelated salt (e.g. ammonium iron EDTA) for use as a polishing accelerator, and a solvent for said salt.
U.S. Pat. No. 5,336,542 discloses a polishing composition comprising alumina abrasive particles and a chelating agent selected from the group consisting of polyaminocarboxylic acid (e.g. EDTA) and sodium and potassium salts thereof The composition may further comprise beohmit or an aluminum salt.
U.S. Pat. No. 5,340,370 discloses a chemical mechanical polishing slurry for tungsten or tungsten nitride film, which comprises an oxidizing agent such as potassium ferricyanide, an abrasive, and water, and has a pH between 2 and 4.
U.S. Pat. No. 5,516,346 discloses a slurry for chemical mechanically polishing a titanium film, said slurry comprising potassium fluoride in a concentration sufficient to complex said titanium film and an abrasive such as silica, and having a pH less than eight.
WO 96/16436 discloses a chemical mechanical polishing slurry which comprises abrasive particles having a median particle diameter less than 0.400 microns, a ferric salt oxidant, and an aqueous surfactant suspension of a mixture of propyleneglycol and methylparaben.
In semiconductor processing, need still exists for abrasive compositions which are more economical and have high polishing performance.
The invention provides a chemical mechanical abrasive composition for use in semiconductor processing, which comprises phosphorous acid and/or a salt thereof as an abrasion enhancer. The chemical mechanical abrasive composition of the invention can be in the form of a slurry which comprises 70-99.5% by weight of an aqueous medium, 0.1-25% by weight of an abrasive, and 0.01-2% by weight of the said abrasion enhancer. The chemical mechanical abrasive composition of the invention may further comprise an abrasion co-enhancer selected from an amino acid, a salt thereof, a carboxylic acid, a salt thereof, or a mixture of the acids and/or salts.
The invention provides a chemical mechanical abrasive composition for use in semiconductor processing, which comprises phosphorous acid and/or a salt thereof as an abrasion enhancer. The chemical mechanical abrasive composition of the invention can be in the form of a slurry which comprises 70-99.5% by weight of an aqueous medium, 0.1-25% by weight, preferably 0.5-15% by weight, more preferably 0.5-8% by weight of an abrasive, and 0.01-2% by weight, preferably 0.03-1% by weight, and more preferably 0.03-0.5% by weight of the said abrasion enhancer. The chemical mechanical abrasive composition of the invention may further comprise an abrasion co-enhancer selected from an amino acid, a salt thereof, a carboxylic acid, a salt, thereof, or a mixture of the acids and/or salts.
If phosphorous acid is added to an abrasive slurry, the abrasion rate achieved by the abrasive slurry can be enhanced. Moreover, if the abrasive slurry further comprises an amino acid or a carboxylic acid, the abrasion rate achieved by the abrasive slurry can be further enhanced. However, it has been found that if only an amino acid or a carboxylic acid is added to an abrasive slurry, the abrasion rate achieved by the abrasive slurry cannot be enhanced. Furthermore, it can be known from the examples hereinafter that phosphorous acid has a better abrasion performance than does phosphoric acid have.
The abrasive used in the abrasive composition of the invention can be any commercially available abrasive agent in particle form, such as SiO2, Al2O3, ZrO2, CeO2, SiC, Fe2O3, TiO2, Si3N4, or a mixture thereof. These abrasive particles normally have a high purity, a high surface area, and a narrow particle size distribution, and thus are suitable for use in abrasive compositions as abrasive agents.
The amino acid or carboxylic acid used in the present invention can be any commercially available one, such as glycine, creatine, alanine, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, malonic acid, glutaric acid, adipic acid, citric acid, malic acid, tartaric acid, or oxalic acid.
The chemical mechanical abrasive composition of the present invention may use water as a medium. In the preparation of the abrasive composition, water, and preferably conventional deionized water, may be used to make the abrasive composition into a slurry.
The chemical mechanical abrasive composition of the present invention may further comprise other ingredients which are conventionally used in chemical mechanical abrasive compositions, only if they do not cause any adverse effect on the abrasive composition of the present invention. Therefore, the chemical mechanical abrasive composition of the present invention may optionally comprise an oxidant conventionally used in the art, or for example, in a copper production process, the abrasive composition of the present invention may include benzotriazole and/or its derivatives to protect copper from rapid corrosion.
The abrasive composition of the present invention can be prepared by any conventional method. For example, an abrasive slurry can be prepared by first adding abrasive particles to water and continuously stirring the mixture with a high shear force until the abrasive particles are completely suspended in water. Thereafter, an additional amount of water is added to the slurry such that the abrasive particles in the slurry are present in the desired solid content. For example, if an abrasive slurry prepared according to the invention contains 70-99.5% by weight of deionized water, the solid content of the s range from 0.5 to 25% by weight, preferably 0.5 to 15% by weight, and more preferably 0.5 to 8% by weight. The additives described above are then introduced into the resultant slurry and the pH of the slurry is adjusted by a base to be in the desired range. For example, when the metal film to be polished is Cu or TaN film, the pH may be adjusted to be in the range of 2.5 to 7.